Since the Renaissance, every century has seen the solution of more mathematical problems than the century before, yet many mathematical problems, both major and minor, still remain unsolved.^{[1]} These unsolved problems occur in multiple domains, including physics, computer science, algebra, analysis, combinatorics, algebraic, discrete and Euclidean geometries, graph, group, model, number, set and Ramsey theories, dynamical systems, partial differential equations, and more. Some problems may belong to more than one discipline of mathematics and be studied using techniques from different areas. Prizes are often awarded for the solution to a long-standing problem, and lists of unsolved problems (such as the list of Millennium Prize Problems) receive considerable attention.

## Contents

- 1 Lists of unsolved problems in mathematics
- 2 Unsolved problems
- 2.1 Algebra
- 2.2 Algebraic geometry
- 2.3 Analysis
- 2.4 Combinatorics
- 2.5 Differential geometry
- 2.6 Discrete geometry
- 2.7 Euclidean geometry
- 2.8 Dynamical systems
- 2.9 Games and puzzles
- 2.10 Graph theory
- 2.11 Group theory
- 2.12 Model theory and formal languages
- 2.13 Number theory
- 2.14 Partial differential equations
- 2.15 Ramsey theory
- 2.16 Set theory
- 2.17 Topology

- 3 Problems solved since 1995
- 4 See also
- 5 References
- 6 Further reading
- 7 External links

## Lists of unsolved problems in mathematics

Over the course of time, several lists of unsolved mathematical problems have appeared.

List | Number of problems | Number unresolved or partially resolved |
Proposed by | Proposed in |
---|---|---|---|---|

Hilbert's problems^{[2]} |
23 | 14 | David Hilbert | 1900 |

Landau's problems^{[3]} |
4 | 4 | Edmund Landau | 1912 |

Taniyama's problems^{[4]} |
36 | - | Yutaka Taniyama | 1955 |

Thurston's 24 questions^{[5]}^{[6]} |
24 | - | William Thurston | 1982 |

Smale's problems | 18 | >11 | Stephen Smale | 1998 |

Millennium Prize problems | 7 | 6^{[7]} |
Clay Mathematics Institute | 2000 |

Simon problems | 15 | <12^{[8]}^{[9]} |
Barry Simon | 2000 |

Unsolved Problems on Mathematics for the 21st Century^{[10]} |
22 | - | Jair Minoro Abe, Shotaro Tanaka | 2001 |

DARPA's math challenges^{[11]}^{[12]} |
23 | - | DARPA | 2007 |

### Millennium Prize Problems

Of the original seven Millennium Prize Problems set by the Clay Mathematics Institute in 2000, six have yet to be solved, as of 2019:^{[7]}

- P versus NP
- Hodge conjecture
- Riemann hypothesis
- Yang–Mills existence and mass gap
- Navier–Stokes existence and smoothness
- Birch and Swinnerton-Dyer conjecture

The seventh problem, the Poincaré conjecture, has been solved.^{[13]} The smooth four-dimensional Poincaré conjecture—that is, whether a four-dimensional topological sphere can have two or more inequivalent smooth structures—is still unsolved.^{[14]}

## Unsolved problems

### Algebra

- Homological conjectures in commutative algebra
- Finite lattice representation problem
- Hilbert's sixteenth problem
- Hilbert's fifteenth problem
- Hadamard conjecture
- Jacobson's conjecture
- Crouzeix's conjecture
- Existence of perfect cuboids and associated cuboid conjectures
- Zauner's conjecture: existence of SIC-POVMs in all dimensions
- Wild Problem: Classification of pairs of
*n*×*n*matrices under simultaneous conjugation and problems containing it such as a lot of classification problems - Köthe conjecture
- Birch–Tate conjecture
- Serre's conjecture II
- Bombieri–Lang conjecture
- Farrell–Jones conjecture
- Bost conjecture
- Rota's basis conjecture
- Uniformity conjecture
- Kaplansky's conjectures
- Kummer–Vandiver conjecture
- Serre's multiplicity conjectures
- Pierce–Birkhoff conjecture
- Eilenberg–Ganea conjecture
- Green's conjecture
- Grothendieck–Katz p-curvature conjecture
- Sendov's conjecture
- Zariski–Lipman conjecture

### Algebraic geometry

- Abundance conjecture
- Bass conjecture
- Deligne conjecture
- Dixmier conjecture
- Fröberg conjecture
- Fujita conjecture
- Hartshorne conjectures
^{[15]} - The Jacobian conjecture
- Manin conjecture
- Maulik–Nekrasov–Okounkov–Pandharipande conjecture on an equivalence between Gromov–Witten theory and Donaldson–Thomas theory
^{[16]} - Nakai conjecture
- Resolution of singularities in characteristic
- Standard conjectures on algebraic cycles
- Section conjecture
- Tate conjecture
- Termination of flips
- Virasoro conjecture
- Weight-monodromy conjecture
- Zariski multiplicity conjecture
^{[17]}

### Analysis

- The four exponentials conjecture on the transcendence of at least one of four exponentials of combinations of irrationals
^{[18]} - Lehmer's conjecture on the Mahler measure of non-cyclotomic polynomials
^{[19]} - The Pompeiu problem on the topology of domains for which some nonzero function has integrals that vanish over every congruent copy
^{[20]} - Schanuel's conjecture on the transcendence degree of exponentials of linearly independent irrationals
^{[18]} - Are (the Euler–Mascheroni constant), π +
*e*, π −*e*, π*e*, π/*e*, π^{e}, π^{√2}, π^{π}, e^{π2}, ln π, 2^{e},*e*^{e}, Catalan's constant, or Khinchin's constant rational, algebraic irrational, or transcendental? What is the irrationality measure of each of these numbers?^{[21]}^{[22]}^{[23]} - Vitushkin's conjecture
- Invariant subspace problem
- Kung–Traub conjecture
^{[24]}

### Combinatorics

- Frankl's union-closed sets conjecture: for any family of sets closed under sums there exists an element (of the underlying space) belonging to half or more of the sets
^{[25]} - The lonely runner conjecture: if runners with pairwise distinct speeds run round a track of unit length, will every runner be "lonely" (that is, be at least a distance from each other runner) at some time?
^{[26]} - Singmaster's conjecture: is there a finite upper bound on the multiplicities of the entries greater than 1 in Pascal's triangle?
^{[27]} - Finding a function to model n-step self-avoiding walks.
^{[28]} - The 1/3–2/3 conjecture: does every finite partially ordered set that is not totally ordered contain two elements
*x*and*y*such that the probability that*x*appears before*y*in a random linear extension is between 1/3 and 2/3?^{[29]} - Give a combinatorial interpretation of the Kronecker coefficients.
^{[30]} - Open questions concerning Latin squares

### Differential geometry

- The filling area conjecture, that a hemisphere has the minimum area among shortcut-free surfaces in Euclidean space whose boundary forms a closed curve of given length
^{[31]} - The Hopf conjectures relating the curvature and Euler characteristic of higher-dimensional Riemannian manifolds
^{[32]} - The spherical Bernstein's problem, a possible generalization of the original Bernstein's problem
- Carathéodory conjecture
- Chern's conjecture (affine geometry)
- Chern's conjecture for hypersurfaces in spheres
- Yau's conjecture
- Yau's conjecture on the first eigenvalue
- Closed curve problem: Find (explicit) necessary and sufficient conditions that determine when, given two periodic functions with the same period, the integral curve is closed.
^{[33]}

### Discrete geometry

- Solving the happy ending problem for arbitrary
^{[34]} - Finding matching upper and lower bounds for
*k*-sets and halving lines^{[35]} - The Hadwiger conjecture on covering
*n*-dimensional convex bodies with at most 2^{n}smaller copies^{[36]} - The Kobon triangle problem on triangles in line arrangements
^{[37]} - The McMullen problem on projectively transforming sets of points into convex position
^{[38]} - Tripod packing
^{[39]} - Ulam's packing conjecture about the identity of the worst-packing convex solid
^{[40]} - Sphere packing problems, including the density of the densest packing in dimensions other than 1, 2, 3, 8 and 24, and its asymptotic behavior for high dimensions
- What is the asymptotic growth rate of wasted space for packing unit squares into a half-integer square?
^{[41]} - Kissing number problem for dimensions other than 1, 2, 3, 4, 8 and 24
^{[42]} - How many unit distances can be determined by a set of n points in the Euclidean plane?
^{[43]}

### Euclidean geometry

- Bellman's lost in a forest problem – find the shortest route that is guaranteed to reach the boundary of a given shape, starting at an unknown point of the shape with unknown orientation
^{[44]} - Danzer's problem and Conway's dead fly problem – do Danzer sets of bounded density or bounded separation exist?
^{[45]} - Dissection into orthoschemes – is it possible for simplices of every dimension?
^{[46]} - The einstein problem – does there exist a two-dimensional shape that forms the prototile for an aperiodic tiling, but not for any periodic tiling?
^{[47]} - The Erdős–Oler conjecture that when is a triangular number, packing circles in an equilateral triangle requires a triangle of the same size as packing circles
^{[48]} - Falconer's conjecture that sets of Hausdorff dimension greater than in must have a distance set of nonzero Lebesgue measure
^{[49]} - Inscribed square problem – does every Jordan curve have an inscribed square?
^{[50]} - The Kakeya conjecture – do -dimensional sets that contain a unit line segment in every direction necessarily have Hausdorff dimension and Minkowski dimension equal to ?
^{[51]} - The Kelvin problem on minimum-surface-area partitions of space into equal-volume cells, and the optimality of the Weaire–Phelan structure as a solution to the Kelvin problem
^{[52]} - Lebesgue's universal covering problem on the minimum-area convex shape in the plane that can cover any shape of diameter one
^{[53]} - Moser's worm problem – what is the smallest area of a shape that can cover every unit-length curve in the plane?
^{[54]} - The moving sofa problem – what is the largest area of a shape that can be maneuvered through a unit-width L-shaped corridor?
^{[55]} - Shephard's problem (a.k.a. Dürer's conjecture) – does every convex polyhedron have a net?
^{[56]} - The Thomson problem – what is the minimum energy configuration of mutually-repelling particles on a unit sphere?
^{[57]} - Uniform 5-polytopes – find and classify the complete set of these shapes
^{[58]} - Covering problem of Rado – if the union of finitely many axis-parallel squares has unit area, how small can the largest area covered by a disjoint subset of squares be?
^{[59]} - Toeplitz' conjecture (open since 1911)
- Atiyah conjecture on configurations

### Dynamical systems

- Collatz conjecture (3
*n*+ 1 conjecture) - Lyapunov's second method for stability – For what classes of ODEs, describing dynamical systems, does the Lyapunov’s second method formulated in the classical and canonically generalized forms define the necessary and sufficient conditions for the (asymptotical) stability of motion?
- Furstenberg conjecture – Is every invariant and ergodic measure for the action on the circle either Lebesgue or atomic?
- Margulis conjecture – Measure classification for diagonalizable actions in higher-rank groups
- MLC conjecture – Is the Mandelbrot set locally connected?
- Weinstein conjecture – Does a regular compact contact type level set of a Hamiltonian on a symplectic manifold carry at least one periodic orbit of the Hamiltonian flow?
- Arnold–Givental conjecture and Arnold conjecture – relating symplectic geometry to Morse theory
- Eremenko's conjecture that every component of the escaping set of an entire transcendental function is unbounded
- Is every reversible cellular automaton in three or more dimensions locally reversible?
^{[60]} - Birkhoff conjecture: if a billiard table is strictly convex and integrable, is its boundary necessarily an ellipse?
^{[61]} - Many problems concerning an outer billiard, for example showing that outer billiards relative to almost every convex polygon have unbounded orbits.
- Quantum unique ergodicity conjecture
^{[62]} - Berry–Tabor conjecture
- Painlevé conjecture

### Games and puzzles

#### Combinatorial games

- Sudoku:
- What is the maximum number of givens for a minimal puzzle?
^{[63]} - How many puzzles have exactly one solution?
^{[63]} - How many minimal puzzles have exactly one solution?
^{[63]}

- What is the maximum number of givens for a minimal puzzle?
- Tic-tac-toe variants:
- Given a width of tic-tac-toe board, what is the smallest dimension such that X is guaranteed a winning strategy?
^{[64]}

- Given a width of tic-tac-toe board, what is the smallest dimension such that X is guaranteed a winning strategy?
- What is the Turing completeness status of all unique elementary cellular automata?

#### Games with imperfect information

### Graph theory

#### Paths and cycles in graphs

- Barnette's conjecture that every cubic bipartite three-connected planar graph has a Hamiltonian cycle
^{[65]} - Chvátal's toughness conjecture, that there is a number t such that every t-tough graph is Hamiltonian
^{[66]} - The cycle double cover conjecture that every bridgeless graph has a family of cycles that includes each edge twice
^{[67]} - The Erdős–Gyárfás conjecture on cycles with power-of-two lengths in cubic graphs
^{[68]} - The linear arboricity conjecture on decomposing graphs into disjoint unions of paths according to their maximum degree
^{[69]} - The Lovász conjecture on Hamiltonian paths in symmetric graphs
^{[70]} - The Oberwolfach problem on which 2-regular graphs have the property that a complete graph on the same number of vertices can be decomposed into edge-disjoint copies of the given graph.
^{[71]}

#### Graph coloring and labeling

- The Erdős–Faber–Lovász conjecture on coloring unions of cliques
^{[72]} - The Gyárfás–Sumner conjecture on χ-boundedness of graphs with a forbidden induced tree
^{[73]} - The Hadwiger conjecture relating coloring to clique minors
^{[74]} - The Hadwiger–Nelson problem on the chromatic number of unit distance graphs
^{[75]} - Jaeger's Petersen-coloring conjecture that every bridgeless cubic graph has a cycle-continuous mapping to the Petersen graph
^{[76]} - The list coloring conjecture that, for every graph, the list chromatic index equals the chromatic index
^{[77]} - The Ringel–Kotzig conjecture on graceful labeling of trees
^{[78]} - The total coloring conjecture of Behzad and Vizing that the total chromatic number is at most two plus the maximum degree
^{[79]}

#### Graph drawing

- The Albertson conjecture that the crossing number can be lower-bounded by the crossing number of a complete graph with the same chromatic number
^{[80]} - The Blankenship–Oporowski conjecture on the book thickness of subdivisions
^{[81]} - Conway's thrackle conjecture
^{[82]} - Harborth's conjecture that every planar graph can be drawn with integer edge lengths
^{[83]} - Negami's conjecture on projective-plane embeddings of graphs with planar covers
^{[84]} - The strong Papadimitriou–Ratajczak conjecture that every polyhedral graph has a convex greedy embedding
^{[85]} - Turán's brick factory problem – Is there a drawing of any complete bipartite graph with fewer crossings than the number given by Zarankiewicz?
^{[86]} - Universal point sets of subquadratic size for planar graphs
^{[87]}

#### Miscellaneous graph theory

- Conway's 99-graph problem: does there exist a strongly regular graph with parameters (99,14,1,2)?
^{[88]} - The Erdős–Hajnal conjecture on large cliques or independent sets in graphs with a forbidden induced subgraph
^{[89]} - The GNRS conjecture on whether minor-closed graph families have embeddings with bounded distortion
^{[90]} - The implicit graph conjecture on the existence of implicit representations for slowly-growing hereditary families of graphs
^{[91]} - Jørgensen's conjecture that every 6-vertex-connected
*K*_{6}-minor-free graph is an apex graph^{[92]} - Meyniel's conjecture that cop number is
^{[93]} - Does a Moore graph with girth 5 and degree 57 exist?
^{[94]} - What is the largest possible pathwidth of an n-vertex cubic graph?
^{[95]} - The reconstruction conjecture and new digraph reconstruction conjecture on whether a graph is uniquely determined by its vertex-deleted subgraphs.
^{[96]}^{[97]} - The second neighborhood problem: does every oriented graph contain a vertex for which there are at least as many other vertices at distance two as at distance one?
^{[98]} - Sumner's conjecture: does every -vertex tournament contain as a subgraph every -vertex oriented tree?
^{[99]} - Tutte's conjectures that every bridgeless graph has a nowhere-zero 5-flow and every Petersen-minor-free bridgeless graph has a nowhere-zero 4-flow
^{[100]} - Vizing's conjecture on the domination number of cartesian products of graphs
^{[101]}

### Group theory

- Is every finitely presented periodic group finite?
- The inverse Galois problem: is every finite group the Galois group of a Galois extension of the rationals?
- For which positive integers
*m*,*n*is the free Burnside group B(*m*,*n*) finite? In particular, is B(2, 5) finite? - Is every group surjunctive?
- Andrews–Curtis conjecture
- Herzog–Schönheim conjecture
- Does generalized moonshine exist?
- Are there an infinite number of Leinster groups?
- Guralnick–Thompson conjecture
^{[102]} - Problems in loop theory and quasigroup theory consider generalizations of groups

### Model theory and formal languages

- Vaught's conjecture
- The Cherlin–Zilber conjecture: A simple group whose first-order theory is stable in is a simple algebraic group over an algebraically closed field.
- The Main Gap conjecture, e.g. for uncountable first order theories, for AECs, and for -saturated models of a countable theory.
^{[103]} - Determine the structure of Keisler's order
^{[104]}^{[105]} - The stable field conjecture: every infinite field with a stable first-order theory is separably closed.
- Is the theory of the field of Laurent series over decidable? of the field of polynomials over ?
- (BMTO) Is the Borel monadic theory of the real order decidable? (MTWO) Is the monadic theory of well-ordering consistently decidable?
^{[106]} - The Stable Forking Conjecture for simple theories
^{[107]} - For which number fields does Hilbert's tenth problem hold?
- Assume K is the class of models of a countable first order theory omitting countably many types. If K has a model of cardinality does it have a model of cardinality continuum?
^{[108]} - Shelah's eventual Categority conjecture: For every cardinal there exists a cardinal such that If an AEC K with LS(K)<= is categorical in a cardinal above then it is categorical in all cardinals above .
^{[103]}^{[109]} - Shelah's categoricity conjecture for : If a sentence is categorical above the Hanf number then it is categorical in all cardinals above the Hanf number.
^{[103]} - Is there a logic L which satisfies both the Beth property and Δ-interpolation, is compact but does not satisfy the interpolation property?
^{[110]} - If the class of atomic models of a complete first order theory is categorical in the , is it categorical in every cardinal?
^{[111]}^{[112]} - Is every infinite, minimal field of characteristic zero algebraically closed? (Here, "minimal" means that every definable subset of the structure is finite or co-finite.)
- Kueker's conjecture
^{[113]} - Does there exist an o-minimal first order theory with a trans-exponential (rapid growth) function?
- Does a finitely presented homogeneous structure for a finite relational language have finitely many reducts?
- Do the Henson graphs have the finite model property?
- The universality problem for C-free graphs: For which finite sets C of graphs does the class of C-free countable graphs have a universal member under strong embeddings?
^{[114]} - The universality spectrum problem: Is there a first-order theory whose universality spectrum is minimum?
^{[115]} - Generalized star height problem

### Number theory

#### General

- Grand Riemann hypothesis
*n*conjecture- Hilbert's ninth problem
- Hilbert's eleventh problem
- Hilbert's twelfth problem
- Carmichael's totient function conjecture
- Erdős–Straus conjecture
- Erdős–Ulam problem
- Pillai's conjecture
- Hall's conjecture
- Lindelöf hypothesis and its consequence, the density hypothesis for zeroes of the Riemann zeta function (see Bombieri–Vinogradov theorem)
- Montgomery's pair correlation conjecture
- Hilbert–Pólya conjecture
- Grimm's conjecture
- Leopoldt's conjecture
- Scholz conjecture
- Do any odd perfect numbers exist?
- Are there infinitely many perfect numbers?
- Do quasiperfect numbers exist?
- Do any odd weird numbers exist?
- Do any Lychrel numbers exist?
- Is 10 a solitary number?
- Catalan–Dickson conjecture on aliquot sequences
- Do any Taxicab(5, 2, n) exist for
*n*> 1? - Brocard's problem: existence of integers, (
*n*,*m*), such that*n*! + 1 =*m*^{2}other than*n*= 4, 5, 7 - Beilinson conjecture
- Littlewood conjecture
- Szpiro's conjecture
- Vojta's conjecture
- Goormaghtigh conjecture
- Congruent number problem (a corollary to Birch and Swinnerton-Dyer conjecture, per Tunnell's theorem)
- Lehmer's totient problem: if φ(
*n*) divides*n*− 1, must*n*be prime? - Are there infinitely many amicable numbers?
- Are there any pairs of amicable numbers which have opposite parity?
- Are there any pairs of relatively prime amicable numbers?
- Are there infinitely many betrothed numbers?
- Are there any pairs of betrothed numbers which have same parity?
- The Gauss circle problem – how far can the number of integer points in a circle centered at the origin be from the area of the circle?
- Piltz divisor problem, especially Dirichlet's divisor problem
- Exponent pair conjecture
- Is π a normal number (its digits are "random")?
^{[116]} - Casas-Alvero conjecture
- Sato–Tate conjecture
- Find value of De Bruijn–Newman constant
- Which integers can be written as the sum of three perfect cubes?
^{[117]} - Erdős–Moser problem: is 1
^{1}+ 2^{1}= 3^{1}the only solution to the Erdős–Moser equation? - Is there a covering system with odd distinct moduli?
^{[118]} - The uniqueness conjecture for Markov numbers
^{[119]} - Keating–Snaith conjecture concerning the asymptotics of an integral involving the Riemann zeta function
^{[120]}

#### Additive number theory

- Beal's conjecture
- Fermat–Catalan conjecture
- Goldbach's conjecture
- The values of
*g*(*k*) and*G*(*k*) in Waring's problem - Lander, Parkin, and Selfridge conjecture
- Gilbreath's conjecture
- Erdős conjecture on arithmetic progressions
- Erdős–Turán conjecture on additive bases
- Pollock octahedral numbers conjecture
- Skolem problem
- Determine growth rate of
*r*_{k}(*N*) (see Szemerédi's theorem) - Minimum overlap problem
- Do the Ulam numbers have a positive density?

#### Algebraic number theory

- Are there infinitely many real quadratic number fields with unique factorization (Class number problem)?
- Characterize all algebraic number fields that have some power basis.
- Stark conjectures (including Brumer–Stark conjecture)
- Kummer–Vandiver conjecture
- Greenberg's conjectures

#### Computational number theory

- Integer factorization: Can integer factorization be done in polynomial time?

#### Prime numbers

- Brocard's Conjecture
- Catalan's Mersenne conjecture
- Agoh–Giuga conjecture
- The Gaussian moat problem: is it possible to find an infinite sequence of distinct Gaussian prime numbers such that the difference between consecutive numbers in the sequence is bounded?
- New Mersenne conjecture
- Erdős–Mollin–Walsh conjecture
- Are there infinitely many prime quadruplets?
- Are there infinitely many cousin primes?
- Are there infinitely many sexy primes?
- Are there infinitely many Mersenne primes (Lenstra–Pomerance–Wagstaff conjecture); equivalently, infinitely many even perfect numbers?
- Are there infinitely many Wagstaff primes?
- Are there infinitely many Sophie Germain primes?
- Are there infinitely many Pierpont primes?
- Are there infinitely many regular primes, and if so is their relative density ?
- For any given integer
*b*which is not a perfect power and not of the form −4*k*^{4}for integer*k*, are there infinitely many repunit primes to base*b*? - Are there infinitely many Cullen primes?
- Are there infinitely many Woodall primes?
- Are there infinitely many Carol primes?
- Are there infinitely many Kynea primes?
- Are there infinitely many palindromic primes to every base?
- Are there infinitely many Fibonacci primes?
- Are there infinitely many Lucas primes?
- Are there infinitely many Pell primes?
- Are there infinitely many Newman–Shanks–Williams primes?
- Are all Mersenne numbers of prime index square-free?
- Are there infinitely many Wieferich primes?
- Are there any Wieferich primes in base 47?
- Are there any composite
*c*satisfying 2^{c − 1}≡ 1 (mod*c*^{2})? - For any given integer
*a*> 0, are there infinitely many primes*p*such that*a*^{p − 1}≡ 1 (mod*p*^{2})?^{[121]} - Can a prime
*p*satisfy 2^{p − 1}≡ 1 (mod*p*^{2}) and 3^{p − 1}≡ 1 (mod*p*^{2}) simultaneously?^{[122]} - Are there infinitely many Wilson primes?
- Are there infinitely many Wolstenholme primes?
- Are there any Wall–Sun–Sun primes?
- For any given integer
*a*> 0, are there infinitely many Lucas–Wieferich primes associated with the pair (*a*, −1)? (Specially, when*a*= 1, this is the Fibonacci-Wieferich primes, and when*a*= 2, this is the Pell-Wieferich primes) - Is every Fermat number 2
^{2n}+ 1 composite for ? - Are all Fermat numbers square-free?
- For any given integer
*a*which is not a square and does not equal to −1, are there infinitely many primes with*a*as a primitive root? - Artin's conjecture on primitive roots
- Is 78,557 the lowest Sierpiński number (so-called Selfridge's conjecture)?
- Is 509,203 the lowest Riesel number?
- Fortune's conjecture (that no Fortunate number is composite)
- Landau's problems
- Feit–Thompson conjecture
- Does every prime number appear in the Euclid–Mullin sequence?
- Does the converse of Wolstenholme's theorem hold for all natural numbers?
- Elliott–Halberstam conjecture
- Problems associated to Linnik's theorem
- Find the smallest Skewes' number

### Partial differential equations

- Regularity of solutions of Vlasov–Maxwell equations
- Regularity of solutions of Euler equations

### Ramsey theory

- The values of the Ramsey numbers, particularly
- The values of the Van der Waerden numbers

### Set theory

- The problem of finding the ultimate core model, one that contains all large cardinals.
- If ℵ
_{ω}is a strong limit cardinal, then 2^{ℵω}< ℵ_{ω1}(see Singular cardinals hypothesis). The best bound, ℵ_{ω4}, was obtained by Shelah using his pcf theory. - Woodin's Ω-hypothesis.
- Does the consistency of the existence of a strongly compact cardinal imply the consistent existence of a supercompact cardinal?
- (Woodin) Does the Generalized Continuum Hypothesis below a strongly compact cardinal imply the Generalized Continuum Hypothesis everywhere?
- Does there exist a Jónsson algebra on ℵ
_{ω}? - Without assuming the axiom of choice, can a nontrivial elementary embedding
*V*→*V*exist? - Does the Generalized Continuum Hypothesis entail for every singular cardinal ?
- Does the Generalized Continuum Hypothesis imply the existence of an ℵ
_{2}-Suslin tree? - Is OCA (Open coloring axiom) consistent with ?
- Assume ZF and that whenever there is a surjection from onto there is an injection from into . Does the Axiom of Choice hold?
^{[123]}

### Topology

- Baum–Connes conjecture
- Borel conjecture
- Hilbert–Smith conjecture
- Mazur's conjectures
^{[124]} - Novikov conjecture
- Unknotting problem
- Volume conjecture
- Whitehead conjecture
- Zeeman conjecture

## Problems solved since 1995

- Hedetniemi's conjecture on the chromatic number of tensor products of graphs (2019)
^{[125]} - Erdős sumset conjecture (2018)
^{[126]} - McMullen's g-conjecture on the possible numbers of faces of different dimensions in a simplicial sphere (also Grünbaum conjecture, several conjectures of Kühnel)
^{[127]}^{[128]} - Pentagonal tiling (Michaël Rao, 2017)
^{[129]} - Erdős–Burr conjecture (Choongbum Lee, 2017)
^{[130]} - Boolean Pythagorean triples problem (Marijn Heule, Oliver Kullmann, Victor Marek, 2016)
^{[131]}^{[132]} - Babai's problem (Problem 3.3 in "Spectra of Cayley graphs") (A. Abdollahi, M. Zallaghi, 2015)
^{[133]} - Main conjecture in Vinogradov's mean-value theorem (Jean Bourgain, Ciprian Demeter, Larry Guth, 2015)
^{[134]} - Erdős discrepancy problem (Terence Tao, 2015)
^{[135]} - Umbral moonshine conjecture (John F. R. Duncan, Michael J. Griffin, Ken Ono, 2015)
^{[136]} - Anderson conjecture (Cheeger, Naber, 2014)
^{[137]} - Gaussian correlation inequality (Thomas Royen, 2014)
^{[138]} - Goldbach's weak conjecture (Harald Helfgott, 2013)
^{[139]}^{[140]}^{[141]} - Kadison–Singer problem (Adam Marcus, Daniel Spielman and Nikhil Srivastava, 2013)
^{[142]}^{[143]}(and the Feichtinger's conjecture, Anderson’s paving conjectures, Weaver’s discrepancy theoretic and conjectures, Bourgain-Tzafriri conjecture and -conjecture) - Virtual Haken conjecture (Agol, Groves, Manning, 2012)
^{[144]}(and by work of Wise also virtually fibered conjecture) - Hsiang–Lawson's conjecture (Brendle, 2012)
^{[145]} - Willmore conjecture (Fernando Codá Marques and André Neves, 2012)
^{[146]} - Beck's 3-permutations conjecture (Newman, Nikolov, 2011)
^{[147]} - Ehrenpreis conjecture (Kahn, Markovic, 2011)
^{[148]} - Hanna Neumann conjecture (Mineyev, 2011)
^{[149]} - Bloch–Kato conjecture (Voevodsky, 2011)
^{[150]}(and Quillen–Lichtenbaum conjecture and by work of Geisser and Levine (2001) also Beilinson–Lichtenbaum conjecture^{[151]}^{[152]}^{[153]}) - Erdős distinct distances problem (Larry Guth, Netz Hawk Katz, 2011)
^{[154]} - Density theorem (Namazi, Souto, 2010)
^{[155]} - Hirsch conjecture (Francisco Santos Leal, 2010)
^{[156]}^{[157]} - Sidon set problem (J. Cilleruelo, I. Ruzsa and C. Vinuesa, 2010)
^{[158]} - Atiyah conjecture (Austin, 2009)
^{[159]} - Kauffman–Harary conjecture (Matmann, Solis, 2009)
^{[160]} - Surface subgroup conjecture (Kahn, Markovic, 2009)
^{[161]} - Scheinerman's conjecture (Jeremie Chalopin and Daniel Gonçalves, 2009)
^{[162]} - Cobordism hypothesis (Jacob Lurie, 2008)
^{[163]} - Full classification of finite simple groups (Harada, Solomon, 2008)
- Geometrization conjecture, proven by Grigori Perelman
^{[164]}in a series of preprints in 2002-2003^{[165]}. - Serre's modularity conjecture (Chandrashekhar Khare and Jean-Pierre Wintenberger, 2008)
^{[166]}^{[167]}^{[168]} - Heterogeneous tiling conjecture (squaring the plane) (Frederick V. Henle and James M. Henle, 2008)
^{[169]} - Normal scalar curvature conjecture and the Böttcher–Wenzel conjecture (Lu, 2007)
^{[170]} - Erdős–Menger conjecture (Aharoni, Berger 2007)
^{[171]} - Road coloring conjecture (Avraham Trahtman, 2007)
^{[172]} - The angel problem (Various independent proofs, 2006)
^{[173]}^{[174]}^{[175]}^{[176]} - Nirenberg–Treves conjecture (Nils Dencker, 2005)
^{[177]}^{[178]} - Lax conjecture (Lewis, Parrilo, Ramana, 2005)
^{[179]} - The Langlands–Shelstad fundamental lemma (Ngô Bảo Châu and Gérard Laumon, 2004)
^{[180]} - Tameness conjecture and Ahlfors measure conjecture (Ian Agol, 2004)
^{[181]} - Robertson–Seymour theorem (Robertson, Seymour, 2004)
^{[182]} - Stanley–Wilf conjecture (Gábor Tardos and Adam Marcus, 2004)
^{[183]}(and also Alon–Friedgut conjecture) - Green–Tao theorem (Ben J. Green and Terence Tao, 2004)
^{[184]} - Ending lamination theorem (Jeffrey F. Brock, Richard D. Canary, Yair N. Minsky, 2004)
^{[185]} - Carpenter's rule problem (Connelly, Demaine, Rote, 2003)
^{[186]} - Cameron–Erdős conjecture (Ben J. Green, 2003, Alexander Sapozhenko, 2003)
^{[187]}^{[188]} - Milnor conjecture (Vladimir Voevodsky, 2003)
^{[189]} - Kemnitz's conjecture (Reiher, 2003, di Fiore, 2003)
^{[190]} - Nagata's conjecture (Shestakov, Umirbaev, 2003)
^{[191]} - Kirillov's conjecture (Baruch, 2003)
^{[192]} - Poincaré conjecture (Grigori Perelman, 2002)
^{[164]} - Strong perfect graph conjecture (Maria Chudnovsky, Neil Robertson, Paul Seymour and Robin Thomas, 2002)
^{[193]} - Kouchnirenko’s conjecture (Haas, 2002)
^{[194]} - Vaught conjecture (Knight, 2002)
^{[195]} - Double bubble conjecture (Hutchings, Morgan, Ritoré, Ros, 2002)
^{[196]} - Catalan's conjecture (Preda Mihăilescu, 2002)
^{[197]} *n*! conjecture (Haiman, 2001)^{[198]}(and also Macdonald positivity conjecture)- Kato's conjecture (Auscher, Hofmann, Lacey, McIntosh and Tchamitchian, 2001)
^{[199]} - Deligne's conjecture on 1-motives (Luca Barbieri-Viale, Andreas Rosenschon, Morihiko Saito, 2001)
^{[200]} - Modularity theorem (Breuil, Conrad, Diamond and Taylor, 2001)
^{[201]} - Erdős–Stewart conjecture (Florian Luca, 2001)
^{[202]} - Berry–Robbins problem (Atiyah, 2000)
^{[203]} - Erdős–Graham problem (Croot, 2000)
^{[204]} - Honeycomb conjecture (Thomas Hales, 1999)
^{[205]} - Gradient conjecture (Krzysztof Kurdyka, Tadeusz Mostowski, Adam Parusinski, 1999)
^{[206]} - Bogomolov conjecture (Emmanuel Ullmo, 1998, Shou-Wu Zhang, 1998)
^{[207]}^{[208]} - Lafforgue's theorem (Laurent Lafforgue, 1998)
^{[209]} - Kepler conjecture (Ferguson, Hales, 1998)
^{[210]} - Dodecahedral conjecture (Hales, McLaughlin, 1998)
^{[211]} - Ganea conjecture (Iwase, 1997)
^{[212]} - Torsion conjecture (Merel, 1996)
^{[213]} - Harary's conjecture (Chen, 1996)
^{[214]} - Fermat's Last Theorem (Andrew Wiles and Richard Taylor, 1995)
^{[215]}^{[216]}

## See also

- List of conjectures
- List of unsolved problems in statistics
- List of unsolved problems in computer science
- List of unsolved problems in physics
- Lists of unsolved problems

## References

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(eds.).*Theory and Applications of Satisfiability Testing – SAT 2016*. Lecture Notes in Computer Science.**9710**. Springer, [Cham]. pp. 228–245. arXiv:1605.00723. doi:10.1007/978-3-319-40970-2_15. ISBN 978-3-319-40969-6. MR 3534782.**^**Abdollahi A., Zallaghi M. (2015). "Character sums for Cayley graphs".*Communications in Algebra*.**43**(12): 5159–5167. doi:10.1080/00927872.2014.967398.**^**Bourgain, Jean; Ciprian, Demeter; Larry, Guth (2015). "Proof of the main conjecture in Vinogradov's Mean Value Theorem for degrees higher than three".*Annals of Mathematics*.**184**(2): 633–682. doi:10.4007/annals.2016.184.2.7. hdl:1721.1/115568.**^**Bruhn, Henning; Schaudt, Oliver (2015). "The Erdos discrepancy problem". arXiv:1509.05363v5 [math.CO].**^**Duncan, John F. R.; Griffin, Michael J.; Ono, Ken (1 December 2015). "Proof of the umbral moonshine conjecture".*Research in the Mathematical Sciences*.**2**(1): 26. doi:10.1186/s40687-015-0044-7.**^**Bruhn, Henning; Schaudt, Oliver (2014). 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American Mathematical Society. pp. 299–355. doi:10.1090/conm/414/07820. ISBN 978-0-8218-3923-2. Retrieved 24 April 2015.**^**Mackenzie, Dana. "Kadison–Singer Problem Solved" (PDF).*SIAM News*(January/February 2014). Society for Industrial and Applied Mathematics. Retrieved 24 April 2015.**^**Bruhn, Henning; Schaudt, Oliver (2012). "The virtual Haken conjecture". arXiv:1204.2810v1 [math.GT].**^**Lee, Choongbum (2012). "Embedded minimal tori in S^3 and the Lawson conjecture". arXiv:1203.6597v2 [math.DG].**^**Marques, Fernando C.; Neves, André (2013). "Min-max theory and the Willmore conjecture".*Annals of Mathematics*.**179**(2): 683–782. arXiv:1202.6036. doi:10.4007/annals.2014.179.2.6.**^**Lee, Choongbum (2011). "A counterexample to Beck's conjecture on the discrepancy of three permutations". arXiv:1104.2922 [cs.DM].**^**Bruhn, Henning; Schaudt, Oliver (2011). "The good pants homology and the Ehrenpreis conjecture". arXiv:1101.1330v4 [math.GT].**^**http://www.math.uiuc.edu/~mineyev/math/art/submult-shnc.pdf**^**http://annals.math.princeton.edu/wp-content/uploads/annals-v174-n1-p11-p.pdf**^**https://www.uni-due.de/~bm0032/publ/BlochKato.pdf**^**"page 359" (PDF).**^**"motivic cohomology – Milnor–Bloch–Kato conjecture implies the Beilinson-Lichtenbaum conjecture – MathOverflow".**^**Bruhn, Henning; Schaudt, Oliver (2010). "On the Erdos distinct distance problem in the plane". arXiv:1011.4105v3 [math.CO].**^**Namazi, Hossein; Souto, Juan (2012). "Non-realizability and ending laminations: Proof of the density conjecture".*Acta Mathematica*.**209**(2): 323–395. doi:10.1007/s11511-012-0088-0.**^**Santos, Franciscos (2012). "A counterexample to the Hirsch conjecture".*Annals of Mathematics*.**176**(1): 383–412. arXiv:1006.2814. doi:10.4007/annals.2012.176.1.7.**^**Ziegler, Günter M. (2012). "Who solved the Hirsch conjecture?".*Documenta Mathematica*. Extra Volume "Optimization Stories": 75–85.**^**Cilleruelo, Javier (2010). "Generalized Sidon sets".*Advances in Mathematics*.**225**(5): 2786–2807. doi:10.1016/j.aim.2010.05.010.**^**Bruhn, Henning; Schaudt, Oliver (2009). "Rational group ring elements with kernels having irrational dimension".*Proceedings of the London Mathematical Society*.**107**(6): 1424–1448. arXiv:0909.2360v3. doi:10.1112/plms/pdt029.**^**Bruhn, Henning; Schaudt, Oliver (2009). "A proof of the Kauffman-Harary Conjecture".*Algebr. Geom. Topol*.**9**(4): 2027–2039. arXiv:0906.1612v2. doi:10.2140/agt.2009.9.2027.**^**Bruhn, Henning; Schaudt, Oliver (2009). "Immersing almost geodesic surfaces in a closed hyperbolic three manifold". arXiv:0910.5501v5 [math.GT].**^**http://www.csie.ntu.edu.tw/~hil/bib/ChalopinG09.pdf**^**Lurie, Jacob (2009). 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^{a}^{b}"Prize for Resolution of the Poincaré Conjecture Awarded to Dr. Grigoriy Perelman" (PDF) (Press release). Clay Mathematics Institute. March 18, 2010. Retrieved November 13, 2015.The Clay Mathematics Institute hereby awards the Millennium Prize for resolution of the Poincaré conjecture to Grigoriy Perelman.

**^**Bruhn, Henning; Schaudt, Oliver (2008). "Completion of the Proof of the Geometrization Conjecture". arXiv:0809.4040 [math.DG].**^**Khare, Chandrashekhar; Wintenberger, Jean-Pierre (2009), "Serre's modularity conjecture (I)",*Inventiones Mathematicae*,**178**(3): 485–504, Bibcode:2009InMat.178..485K, CiteSeerX 10.1.1.518.4611, doi:10.1007/s00222-009-0205-7**^**Khare, Chandrashekhar; Wintenberger, Jean-Pierre (2009), "Serre's modularity conjecture (II)",*Inventiones Mathematicae*,**178**(3): 505–586, Bibcode:2009InMat.178..505K, CiteSeerX 10.1.1.228.8022, doi:10.1007/s00222-009-0206-6**^**"2011 Cole Prize in Number Theory" (PDF).*Notices of the AMS*.**58**(4): 610–611. ISSN 1088-9477. OCLC 34550461.**^**http://www.ww.amc12.org/sites/default/files/pdf/pubs/SquaringThePlane.pdf**^**Lu, Zhiqin (2007). "Proof of the normal scalar curvature conjecture". arXiv:0711.3510 [math.DG].**^**Bruhn, Henning; Schaudt, Oliver (2005). "Menger's theorem for infinite graphs". arXiv:math/0509397.**^**Seigel-Itzkovich, Judy (2008-02-08). "Russian immigrant solves math puzzle".*The Jerusalem Post*. Retrieved 2015-11-12.**^**http://homepages.warwick.ac.uk/~masgak/papers/bhb-angel.pdf**^**http://home.broadpark.no/~oddvark/angel/Angel.pdf**^**http://homepages.warwick.ac.uk/~masibe/angel-mathe.pdf**^**http://www.cs.bu.edu/~gacs/papers/angel.pdf**^**Dencker, Nils (2006), "The resolution of the Nirenberg–Treves conjecture" (PDF),*Annals of Mathematics*,**163**(2): 405–444, doi:10.4007/annals.2006.163.405**^**"Research Awards",*Clay Mathematics Institute*, retrieved 2019-04-07**^**http://www.ams.org/journals/proc/2005-133-09/S0002-9939-05-07752-X/S0002-9939-05-07752-X.pdf**^**"Fields Medal – Ngô Bảo Châu".*International Congress of Mathematicians 2010*. ICM. 19 August 2010. Retrieved 2015-11-12.Ngô Bảo Châu is being awarded the 2010 Fields Medal for his proof of the Fundamental Lemma in the theory of automorphic forms through the introduction of new algebro-geometric methods.

**^**Bruhn, Henning; Schaudt, Oliver (2004). "Tameness of hyperbolic 3-manifolds". arXiv:math/0405568.**^**"Graph Theory".**^**Chung, Fan; Greene, Curtis; Hutchinson, Joan (April 2015). "Herbert S. Wilf (1931–2012)" (PDF).*Notices of the AMS*.**62**(4): 358. ISSN 1088-9477. OCLC 34550461.The conjecture was finally given an exceptionally elegant proof by A. Marcus and G. Tardos in 2004.

**^**"Bombieri and Tao Receive King Faisal Prize" (PDF).*Notices of the AMS*.**57**(5): 642–643. May 2010. ISSN 1088-9477. OCLC 34550461.Working with Ben Green, he proved there are arbitrarily long arithmetic progressions of prime numbers—a result now known as the Green–Tao theorem.

**^**Bruhn, Henning; Schaudt, Oliver (2004). "The classification of Kleinian surface groups, II: The Ending Lamination Conjecture". arXiv:math/0412006.**^**Connelly, Robert; Demaine, Erik D.; Rote, Günter (2003), "Straightening polygonal arcs and convexifying polygonal cycles" (PDF),*Discrete and Computational Geometry*,**30**(2): 205–239, doi:10.1007/s00454-003-0006-7, MR 1931840**^**Green, Ben (2004), "The Cameron–Erdős conjecture",*The Bulletin of the London Mathematical Society*,**36**(6): 769–778, arXiv:math.NT/0304058, doi:10.1112/S0024609304003650, MR 2083752**^**"News from 2007".*American Mathematical Society*. AMS. 31 December 2007. Retrieved 2015-11-13.The 2007 prize also recognizes Green for "his many outstanding results including his resolution of the Cameron-Erdős conjecture..."

**^**Voevodsky, Vladimir (2003). "Reduced power operations in motivic cohomology" (PDF).*Publications Mathématiques de l'IHÉS*.**98**: 1–57. CiteSeerX 10.1.1.170.4427. doi:10.1007/s10240-003-0009-z.**^**Savchev, Svetoslav (2005). "Kemnitz' conjecture revisited".*Discrete Mathematics*.**297**(1���3): 196–201. doi:10.1016/j.disc.2005.02.018.**^**http://www.ams.org/journals/jams/2004-17-01/S0894-0347-03-00440-5/S0894-0347-03-00440-5.pdf**^**http://annals.math.princeton.edu/wp-content/uploads/annals-v158-n1-p04.pdf**^**Chudnovsky, Maria; Robertson, Neil; Seymour, Paul; Thomas, Robin (2002). "The strong perfect graph theorem". arXiv:math/0212070.**^**http://www.emis.de/journals/BAG/vol.43/no.1/b43h1haa.pdf**^**Knight, R. W. (2002), The Vaught Conjecture: A Counterexample, manuscript**^**http://www.ugr.es/~ritore/preprints/0406017.pdf**^**Metsänkylä, Tauno (5 September 2003). "Catalan's conjecture: another old diophantine problem solved" (PDF).*Bulletin of the American Mathematical Society*.**41**(1): 43–57. doi:10.1090/s0273-0979-03-00993-5. ISSN 0273-0979.The conjecture, which dates back to 1844, was recently proven by the Swiss mathematician Preda Mihăilescu.

**^**http://www.ams.org/journals/jams/2001-14-04/S0894-0347-01-00373-3/S0894-0347-01-00373-3.pdf**^**http://junon.u-3mrs.fr/monniaux/AHLMT02.pdf**^**Bruhn, Henning; Schaudt, Oliver (2001). "Deligne's Conjecture on 1-Motives". arXiv:math/0102150.**^**Breuil, Christophe; Conrad, Brian; Diamond, Fred; Taylor, Richard (2001), "On the modularity of elliptic curves over**Q**: wild 3-adic exercises",*Journal of the American Mathematical Society*,**14**(4): 843–939, doi:10.1090/S0894-0347-01-00370-8, ISSN 0894-0347, MR 1839918**^**Luca, Florian (2000). "On a conjecture of Erdős and Stewart" (PDF).*Mathematics of Computation*.**70**(234): 893–897. doi:10.1090/s0025-5718-00-01178-9.**^**http://intlpress.com/site/pub/files/_fulltext/journals/sdg/2002/0007/0001/SDG-2002-0007-0001-a001.pdf**^**Croot, Ernest S., III (2000),*Unit Fractions*, Ph.D. thesis, University of Georgia, Athens. Croot, Ernest S., III (2003), "On a coloring conjecture about unit fractions",*Annals of Mathematics*,**157**(2): 545–556, arXiv:math.NT/0311421, doi:10.4007/annals.2003.157.545**^**Bruhn, Henning; Schaudt, Oliver (1999). "The Honeycomb Conjecture". arXiv:math/9906042.**^**Bruhn, Henning; Schaudt, Oliver (1999). "Proof of the gradient conjecture of R. Thom". arXiv:math/9906212.**^**Ullmo, E (1998). "Positivité et Discrétion des Points Algébriques des Courbes".*Annals of Mathematics*.**147**(1): 167–179. doi:10.2307/120987. JSTOR 120987. Zbl 0934.14013.**^**Zhang, S.-W. (1998). "Equidistribution of small points on abelian varieties".*Annals of Mathematics*.**147**(1): 159–165. doi:10.2307/120986. JSTOR 120986.**^**Lafforgue, Laurent (1998), "Chtoucas de Drinfeld et applications" [Drinfelʹd shtukas and applications],*Documenta Mathematica*(in French),**II**: 563–570, ISSN 1431-0635, MR 1648105**^**Bruhn, Henning; Schaudt, Oliver (2015). "A formal proof of the Kepler conjecture". arXiv:1501.02155 [math.MG].**^**Bruhn, Henning; Schaudt, Oliver (1998). "A proof of the dodecahedral conjecture". arXiv:math/9811079.**^**Norio Iwase (1 November 1998). "Ganea's Conjecture on Lusternik-Schnirelmann Category".*ResearchGate*.**^**Merel, Loïc (1996). ""Bornes pour la torsion des courbes elliptiques sur les corps de nombres" [Bounds for the torsion of elliptic curves over number fields]".*Inventiones Mathematicae*.**124**(1): 437–449. Bibcode:1996InMat.124..437M. doi:10.1007/s002220050059. MR 1369424.**^**Chen, Zhibo (1996). "Harary's conjectures on integral sum graphs".*Discrete Mathematics*.**160**(1–3): 241–244. doi:10.1016/0012-365X(95)00163-Q.**^**Wiles, Andrew (1995). "Modular elliptic curves and Fermat's Last Theorem" (PDF).*Annals of Mathematics*.**141**(3): 443–551. CiteSeerX 10.1.1.169.9076. doi:10.2307/2118559. JSTOR 2118559. OCLC 37032255.**^**Taylor R, Wiles A (1995). "Ring theoretic properties of certain Hecke algebras".*Annals of Mathematics*.**141**(3): 553–572. CiteSeerX 10.1.1.128.531. doi:10.2307/2118560. JSTOR 2118560. OCLC 37032255.

## Further reading

### Books discussing problems solved since 1995

- Singh, Simon (2002).
*Fermat's Last Theorem*. Fourth Estate. ISBN 978-1-84115-791-7. - O'Shea, Donal (2007).
*The Poincaré Conjecture*. Penguin. ISBN 978-1-84614-012-9. - Szpiro, George G. (2003).
*Kepler's Conjecture*. Wiley. ISBN 978-0-471-08601-7. - Ronan, Mark (2006).
*Symmetry and the Monster*. Oxford. ISBN 978-0-19-280722-9.

### Books discussing unsolved problems

- Chung, Fan; Graham, Ron (1999).
*Erdös on Graphs: His Legacy of Unsolved Problems*. AK Peters. ISBN 978-1-56881-111-6. - Croft, Hallard T.; Falconer, Kenneth J.; Guy, Richard K. (1994).
*Unsolved Problems in Geometry*. Springer. ISBN 978-0-387-97506-1. - Guy, Richard K. (2004).
*Unsolved Problems in Number Theory*. Springer. ISBN 978-0-387-20860-2. - Klee, Victor; Wagon, Stan (1996).
*Old and New Unsolved Problems in Plane Geometry and Number Theory*. The Mathematical Association of America. ISBN 978-0-88385-315-3. - du Sautoy, Marcus (2003).
*The Music of the Primes: Searching to Solve the Greatest Mystery in Mathematics*. Harper Collins. ISBN 978-0-06-093558-0. - Derbyshire, John (2003).
*Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics*. Joseph Henry Press. ISBN 978-0-309-08549-6. - Devlin, Keith (2006).
*The Millennium Problems – The Seven Greatest Unsolved* Mathematical Puzzles Of Our Time*. Barnes & Noble. ISBN 978-0-7607-8659-8. - Blondel, Vincent D.; Megrestski, Alexandre (2004).
*Unsolved problems in mathematical systems and control theory*. Princeton University Press. ISBN 978-0-691-11748-5. - Ji, Lizhen; Poon, Yat-Sun; Yau, Shing-Tung (2013).
*Open Problems and Surveys of Contemporary Mathematics (volume 6 in the Surveys in Modern Mathematics series) (Surveys of Modern Mathematics)*. International Press of Boston. ISBN 978-1-57146-278-7. - Waldschmidt, Michel (2004). "Open Diophantine Problems" (PDF).
*Moscow Mathematical Journal*.**4**(1): 245–305. doi:10.17323/1609-4514-2004-4-1-245-305. ISSN 1609-3321. Zbl 1066.11030. - Mazurov, V. D.; Khukhro, E. I. (1 Jun 2015). "Unsolved Problems in Group Theory. The Kourovka Notebook. No. 18 (English version)". arXiv:1401.0300v6 [math.GR].

## External links

- 24 Unsolved Problems and Rewards for them
- List of links to unsolved problems in mathematics, prizes and research
- Open Problem Garden The collection of open problems in mathematics build on the principle of user editable ("wiki") site
- AIM Problem Lists
- Unsolved Problem of the Week Archive. MathPro Press.
- Ball, John M. "Some Open Problems in Elasticity" (PDF).
- Constantin, Peter. "Some open problems and research directions in the mathematical study of fluid dynamics" (PDF).
- Serre, Denis. "Five Open Problems in Compressible Mathematical Fluid Dynamics" (PDF).
- Unsolved Problems in Number Theory, Logic and Cryptography
- 200 open problems in graph theory
- The Open Problems Project (TOPP), discrete and computational geometry problems
- Kirby's list of unsolved problems in low-dimensional topology
- Erdös' Problems on Graphs
- Unsolved Problems in Virtual Knot Theory and Combinatorial Knot Theory
- Open problems from the 12th International Conference on Fuzzy Set Theory and Its Applications
- List of open problems in inner model theory
- Aizenman, Michael. "Open Problems in Mathematical Physics".
- Barry Simon's 15 Problems in Mathematical Physics